This invention relates generally to antenna assemblies that may be used to transmit and receive electro-magnetic radiation signals. More specifically, the invention relates to radio frequency (RF) antenna structures that may be used as sub-components, called subarrays, for electronically scanned arrays (ESAs) made up of a plurality of subarrays.
Electronically scanned arrays (ESAs) are made up of a plurality of antenna radiating elements or radiators, which together form a radiating surface. In one prior ESA implementation, each antenna subarray is configured with a plurality of radiators which are mounted on machined metal support structures. The radiators are located on precise and uniform spacings across the face of the antenna aperture. The radiators are connected to transmit and/or receive (T/R) components that are combined via an radio frequency (RF) distribution manifold. Phase shifters are provided to allow electronic steering of the antenna beam. Phase shifters may be a variety of devices, such as PIN diodes, MMIC""s, ferrite phasors, or other phase shifting devices. Separate DC power and control signals are typically provided to the phase shifters or T/R components through distribution manifolds. A cooling manifold is also typically provided for dissipating heat generated by the phase shifter, T/R components, the DC and control manifold devices.
T/R components may be located immediately behind the ESA radiators to form an Active ESA (AESA). Alternatively, these T/R components may be located remote to the radiators to form a Passive ESA (PESA). Examples of RF generators in a PESA include traveling wave tube (TWT), magnetrons, or solid state transmitter (SST) components. In an AESA configuration, T/R components are usually located in hermetically sealed modules (T/R modules). RF losses are minimized in AESA configurations due to the close proximity of the T/R modules to the radiators. However, the requirement of having a discrete T/R module at each radiator site is costly. In a PESA configuration, the T/R components may be lumped together for more cost-efficient packaging because they are remote to the radiators. However, because these devices are remote from the radiators, increased RF losses tend to lower the overall system performance.
Although ESAs offer many advantages over mechanically scanned antennas, in many applications it is prohibitively expensive to substitute either AESA or PESA equipment for an equal performance mechanically scanned antenna. The most costly components of AESAs generally include the T/R modules and manifold structure required for the T/R modules. The most costly components of PESAs generally include the RF generator, phase shifters, distribution manifolding and structure required for the phase shifters. These problems reduce the cost competitiveness of ESAs compared to mechanically scanned antennas.
In accordance with the present invention, an antenna structure and associated method are disclosed that provide a lightweight and reduced cost subarray. The antenna structure of the present invention may be utilized as a subarray for an ESA system. The antenna structure may include a printed circuit board material coupled to a support structure. The printed circuit board may include electrical circuitry patterns and may have components mounted thereon to provide desired transmit and receive functionality, along with phase shifter and control circuitry. The support structure may be any support material, for example, a foam material that is both strong and lightweight. The combined antenna subarray structure of the present invention may thereby forms a strong, rigid and lightweight antenna component that may be used in an ESA system.
In one embodiment, the present invention is an antenna assembly, including a support structure having a surface and a circuit board coupled to the surface of the support structure, wherein the circuit board includes antenna circuitry. In further embodiments, the antenna circuitry includes electromagnetic radiation transmit and receive circuitry for radio frequency transmissions, and is lightweight material, such as expanded foam. Still further, the circuit board may have conductive structures that have been formed through a screen printing, etch or write process.
In another embodiment, the present invention is an antenna array, including a plurality of antenna assemblies, with each antenna assembly including a support structure and a circuit board coupled to the support structure, wherein the circuit board includes antenna circuitry and wherein the plurality of antenna assemblies communicate to provide an antenna array. In further embodiments, each antenna assembly further includes phase control circuitry that electrically adjusts a direction for transmission and receipt of electromagnetic radiation. Also, the connections for the phase control circuitry may be formed on the circuit boards through a screen printing, etch or write process.
In yet another embodiment, the present invention is a method for operating an antenna array, including transmitting and/or receiving electromagnetic radiation signals with a plurality of antenna assemblies, wherein each antenna assembly includes a support structure and a circuit board with antenna circuitry coupled to a surface of the support structure, and utilizing the signals received and/or transmitted by the antenna assemblies to form an array of transmitted and/or received signals. In a further embodiment, the present invention includes providing phase control circuitry that electrically adjusts a direction for the transmission or receipt of electromagnetic radiation.
Furthermore, the present invention is a radio frequency (RF)antenna assembly, including a substantially light weight support structure having first and second opposing support structure surfaces, a first circuit board having first and second opposing circuit board surfaces, wherein at least a portion of the second surface of the first circuit board is coupled to at least a portion of the first surface of the support structure, at least one of the first or second surfaces of the first circuit board having conductive RF transmission circuitry defined thereon, and at least one of the first or second surfaces of the first circuit board having conductive ground plane circuitry defined thereon. In this embodiment, the RF transmission circuitry and the ground plane circuitry are spaced in operative relationship to form at least one antenna radiating element, and the radiating element is coupled to at least a portion of the first or second surfaces of the first circuit board in operative relationship with the RF transmission circuitry and the conductive ground plane circuitry. In a more detailed respect, the RF antenna further includes a second circuit board having first and second opposing circuit board surfaces, wherein at least a portion of the second surface of the second circuit board being coupled to at least a portion of the support structure second surface, at least one of the first or second surfaces of the second circuit board having conductive RF transmission circuitry defined thereon, and at least one of the first or second surfaces of the second circuit board having conductive ground plane circuitry defined thereon
In another embodiment, the present invention is an electronically scanned array, including a plurality of subarray elements, where each of the subarray elements includes a substantially lightweight support structure having first and second opposing support structure surfaces, a first circuit board having first and second opposing circuit board surfaces, and a second circuit board having first and second opposing circuit board surfaces. In this embodiment, the first circuit board has at least a portion of its second surface being coupled to at least a portion of the first surface of the support structure, its first surface having copper RF transmission circuitry, and its second surface having a copper ground plane circuitry defined thereon. The second circuit board has at least a portion of its second surface coupled to at least a portion of the second surface of the support structure surface, its first surface having copper RF transmission circuitry, and its second surface having copper ground plane circuitry defined thereon. In addition, the RF transmission circuitry and the ground plane circuitry for the first and second circuit boards are spaced in operative relationship to form first antenna radiating elements. Also, control and DC power circuitry are defined on the first surfaces of the first and second circuit boards. An RF T/R component is electronically coupled to each of the antenna radiating elements, where each of the T/R components includes at least one of a transmitting component, a receiving component, or a mixture thereof In a further embodiment, the RF antenna assembly includes a phase shifter element electronically coupled between each RF T/R component and one or more respective antenna radiating elements. Still further, the phase shifter may comprise at least one phase shifting element comprising a micro-electro-mechanical switch.